In recent years, miniaturization and low power consumption of a radio communication apparatus have been developed. Although the power supply voltage has been lowered following the development of semiconductor process, it is widely known that the linearity of an analogue circuit is deteriorated due to the reduction of the power supply voltage. Furthermore, many radio standards, such as an integrated services digital broadcasting-terrestrial (ISDB-T), is required to receive even under the condition where a strong neighboring interfering wave is present. Therefore, there is a growing demand for distortion compensation in order to improve the linearity at a receiver.
There is a conventional distortion compensation receiver shown in FIG. 1 (for example, see non-patent literature 1). In FIG. 1, distortion compensation receiver 10 has low noise amplifier (LNA) 11, cubic circuit 12, down mixers 13-1 and 13-2, local oscillator (LO) 14, analog low pass filters (LPFs) 15-1 and 15-2, analog-to-digital converters (ADCs) 16-1 and 16-2, digital LPFs 17-1 and 17-2, adaptive filter 18, and adder 19.
Conventional distortion compensation receiver 10 shown in FIG. 1 is divided an input signal into two paths, the original reception circuit (main path) and the path (replica path) for generating a replica signal of distortion. Next, by cubing a replica path, distortion compensation receiver 10 generates a replica signal of a third-order distortion component (inter modulation (IM) 3). Next, distortion compensation receiver 10 frequency-converts this replica signal by down mixer 13-2, extracts a reception band component from the replica signal by band-limiting by LPF 15-2. Next, distortion compensation receiver 10 allows this extracted signal to pass adaptive filter 18 and then subtracts the extracted signal from the main path signal. By this means, distortion compensation receiver 10 reduces a third-order distortion component included in the main path signal.
There is other distortion compensation receiver shown in FIG. 2 (for example, see non-patent literature 2). In FIG. 2, distortion compensation receiver 20 has nonlinear circuit 21, band division filter 22, distortion generation circuit 23, band limitation filter 24, adaptive filter 25, delayer 26, and adder 27.
With conventional distortion compensation receiver 20 shown in FIG. 2, band division filter 22 divides a signal amplified by nonlinear circuit 21 into a desired band signal and other band signal. Distortion generation circuit 23 generates a replica signal of distortion component (IM) by using a signal of a band other than the desired band. A replica signal is band-limited at band limitation filter 24. Later, by subtracting a band-limited replica signal from the main path signal that is output from delayer 26 after passing adaptive filter 25, distortion compensation receiver 20 reduces nonlinear distortion included in the main path signal.